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Slide 1

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ENZYMES
· Biological catalysts
· Can be intra or extracellular
· Globular proteins
· Have an active site complimentary (specific) to
the substrate
· Tertiary structure determines the active site
· Reduce activation energy…read more

Slide 2

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TWO MODELS
· LOCK AND KEY: Substrate fits exactly into
active site
· Like a key fits into a lock exactly
· INDUCED FIT: A more accurate description
· The substrate causes the active site to change
shape slightly, so that it binds even tighter
· This puts greater strain on the substrate, so
the reaction is quicker…read more

Slide 3

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TEMPERATURE
· A higher temperature means molecules have more
kinetic energy
· More collisions between substrate and active site
occur, so the reaction rate rises
· However the molecules in the enzyme also vibrate
more
· If strong enough, this can break the hydrogen and
ionic bonds holding the active site in shape
· This prevents the reaction from taking place as the
active site has to be a specific shape, and the
reaction rate falls. The enzyme becomes denatured…read more

Slide 4

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pH
· All enzymes have an optimum pH
· This depends on the environment that the
enzyme is in
· A lower pH means there are more H+ ions
· A higher pH means there are more OH- ions
· These interfere with the bonds holding the
active site in shape
· This makes the active site change shape, so
the substrate can no longer bind, and the
enzyme becomes denatured.…read more

Slide 5

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ENZYME CONCENTRATION
· If there are more enzymes, more collisions
occur, more enzyme-substrate complexes
form and so more products form & the
reaction rate rises
· However if the substrate amount is limited,
then after a while there will be more enzymes
than substrates, so the reaction rate will not
rise any higher, as no more enzyme-substrate
complexes will form.…read more

Slide 6

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SUBSTRATE CONCENTRATION
· If there are more substrates, more collisions
with the active sites will occur, more enzyme-
substrate complexes will form and so more
products will form and the reaction rate rises
· However after a while there will be more
substrates than enzymes, and all the active
sites are full, so adding more substrate does
not increase the reaction rate.…read more

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